This celebrated riddle of the Sphinx was not a very difficult one. It was as follows: "A being with four feet has two feet and three feet; but its feet vary, and when it has most it is weakest."
The answer, as given by Œdipus, was "Man," who
"First as a babe four-footed creeps on his way,
Then, when full age cometh on, and the burden of years weighs full heavy,
Bending his shoulders and neck, as a third foot useth his staff."
When the truth became known—as truth was apt to become known when too late in old stories—the queen, Jocasta, mad with anguish, hanged herself, and Œdipus, in wild despair, put out his eyes. The gods who had led him blindly into crime, now handed him over to punishment by the Furies,—the ancient goddesses of vengeance, whose mission it was to pursue the criminal with stinging whips.
The tragic events which followed arose from the curse of the afflicted Œdipus. He had two sons, Polynikes and Eteocles, who twice offended him without intention, and whom he, frenzied by his troubles, twice bitterly cursed, praying to the gods that they might perish by each other's hands. Œdipus afterwards obtained the pardon of the gods for his involuntary crime, and died in exile, leaving Creon, the brother of Jocasta, on the throne. But though he was dead, his curse kept alive, and brought on new matter of dire moment.
It began its work in a quarrel between the two sons as to who should succeed their uncle as king of Thebes. Polynikes was in the wrong, and was forced to leave Thebes, while Eteocles remained. The exiled prince sought the court of Adrastus, king of Argos, who gave him his daughter in marriage, and agreed to assist in restoring him to his native country.
Most of the Argive chiefs joined in the proposed expedition. But the most distinguished of them all, Amphiaraüs, opposed it as unjust and against the will of the gods. He concealed himself, lest he should be forced into the enterprise. But the other chiefs deemed his aid indispensable, and bribed his wife, with a costly present, to reveal his hiding-place. Amphiaraüs was thus forced to join the expedition, but his prophetic power taught him that it would end in disaster to all and death to himself, and as a measure of revenge he commanded his son Alkmæon to kill the faithless woman who had betrayed him, and after his death to organize a second expedition against Thebes.
Seven chiefs led the army, one to assail each of the seven celebrated gates of Thebes. Onward they marched against that strong city, heedless of the hostile portents which they met on their way. The Thebans also sought the oracle of the gods, and were told that they should be victorious, but only on the dread condition that Creon's son, Menœceus, should sacrifice himself to Mars. The devoted youth, on learning that the safety of his country depended on his life, forthwith killed himself before the city gates,—thus securing by innocent blood the powerful aid of the god of war.